Kawai K4 Synthesizer
This page documents my fascination with this interesting and seemingly overlooked jewel from the same era as the Roland D-50 and Korg M1.
|"The K4 from Kawai can be thought of as a warm and fuzzy digital synthesizer. A sample-based digital synth, its sounds are those typically weird industrial type sounds that can still be useful in lo-fi, big-beat and trip hop music styles. The sounds are 16-bit preset PCM samples of acoustic instruments. However, unlike its predecessor the K1, the K4 adds a welcomed digital filter section. This truly makes the K4 more flexible, fun and useful for today's filter tweaking music effects!"
Vintage Synth Explorer
While there are quite a few examples of the K4 on YouTube,
this one in
particular captures a lot of the warmth and breadth of this synth.
This track shows off what some clever programmging on the K4 can achieve:
Soundbank Demo (Soundcloud)
The K4 uses an NEC 78KIII series microcontroller, a uPD78310. I've
managed to source some datasheets and other documents from the web.
Understanding How It Works
I couldn't resist it. After a few weeks hacking away I now have a
disassembler for the uPD78310. It is part of the
You will need to get hold of a ROM image,
either from a ROM pulled from a K4, or the latest ROM image from Kawai
(see below). If you do the latter, convert the Motorola S-REC files
into plain binary (I use the
srecord tool). Then you are
ready to run the raw binary through
dasm78k3 once you have
a disassembler command file. My own is presented as a work-in-progress:
As I begin to explore the code, I also had to work out the memory layout.
Most of it is conventional:
- 0000-7FFF = ROM
- 8000-BFFF = paged RAM/card/ROM
- C000-DFFF = RAM
- E000-FDFF = external hardware blocks (sound engine, DSP, etc)
- FE00-FFFF = internal memory and registers
The paged memory block (8000-BFFF) is controlled by two I/O pins P35 and P34 (pin 5 and pin 4 of Port 3 respectively):
|ROM (region 8000-BFFF)
|ROM (region C000-FFFF)
The service manual can be purchased from
W D Greenhill.
Although you may baulk at paying for something you can find online I can
say that the copy from Greenhill is of a much higher quality than what I have
found online so far.
It is still possible to download the latest revision 1.4 ROM images from Kawai:
They are in Motorola S19 format, and you'll need a blank EPROM and suitable
programmer to burn a new ROM.
First and foremost, the factory reset patches are
available from Kawai (click on the link, choose "K4 / K4r" and download the ZIP file, then play the k4.mid file after you've set your MIDI output to point to the K4).
Editors / Librarians